Thermal right, land left

Robertmudd1u wrote:

Some may think this a cheap shot, but what the heck.

Believe it or not some pilots fly gliders with fixed gear. They even fly them
X-C and make land outs. They even stall/spin them.

Too many people in this sport think you need ALL the bells and whistles and a
$100,000+ glider to be a "real" glider pilot. That attitude is hurting us.

Robert Mudd

I certainly would not use the word "need" with respect to a
glider AOA indicator.

And yes, cheap and simple is important. Perhaps the cheapest idea
is simply the ol' harmonica style Cezzna AOA indicators, one
mounted on each wingtip of a 1-26 (easier to install on a metal wing,
and the 1-26 is a glider with more than it's share of stalls
leading to fatalities).

Then, if added complexity is warranted, a small switch on the
spoilers which deactivates the audio vario when the spoilers are out,
so one can now just barely hear the stall horns.

Ideally, it would be nice to have removable wingtips, so
one could experiment without modifying a whole wing...

Perhaps there are other types that would have this feature
to allow inexpensive experimentation. Then maybe try the electric
AOA tabs too...

--

------------+
Mark Boyd
Avenal, California, USA

"Mark James Boyd" wrote in message
news:4054b43e$1@darkstar...
Robertmudd1u wrote:

Some may think this a cheap shot, but what the heck.

Believe it or not some pilots fly gliders with fixed gear. They even fly
them
X-C and make land outs. They even stall/spin them.

Too many people in this sport think you need ALL the bells and whistles
and a
$100,000+ glider to be a "real" glider pilot. That attitude is hurting
us.

Robert Mudd

I certainly would not use the word "need" with respect to a
glider AOA indicator.

And yes, cheap and simple is important. Perhaps the cheapest idea
is simply the ol' harmonica style Cezzna AOA indicators, one
mounted on each wingtip of a 1-26 (easier to install on a metal wing,
and the 1-26 is a glider with more than it's share of stalls
leading to fatalities).

Then, if added complexity is warranted, a small switch on the
spoilers which deactivates the audio vario when the spoilers are out,
so one can now just barely hear the stall horns.

Ideally, it would be nice to have removable wingtips, so
one could experiment without modifying a whole wing...

Perhaps there are other types that would have this feature
to allow inexpensive experimentation. Then maybe try the electric
AOA tabs too...

--

------------+
Mark Boyd
Avenal, California, USA

Tape two yaw strings (which then become pitch strings) on each side of the
canopy at the lowest and most forward part you can still see. Fly once with
a grease pencil to mark the inside of the canopy at the string positions for
best L/D, minimum sink, and stall. By using a string on each side of the
canopy, the error introduced by inadvertent yaw is obvious and can be
eliminated with rudder.

The string position for best L/D, min sink, and stall will always be the
same whether the glider is ballasted, empty or in a steep turn - although
the airspeeds will be very different.

The string angle difference between minimum sink and stall is large so the
bright red, wiggling strings angled up steeply are a good visual stall
warning.

Bill Daniels

"Bill Daniels" wrote:

Tape two yaw strings (which then become pitch strings) on each side of the
canopy at the lowest and most forward part you can still see.

The string angle difference between minimum sink and stall is large so the
bright red, wiggling strings angled up steeply are a good visual stall
warning.

That must be true only for unflapped gliders, or it's valid only for
one specific flap setting in a flapped glider. Or you have to make
different coloured markings for each and every flap setting.

Aldo Cernezzi

"cernauta" wrote in message
...
"Bill Daniels" wrote:

Tape two yaw strings (which then become pitch strings) on each side of
the
canopy at the lowest and most forward part you can still see.

The string angle difference between minimum sink and stall is large so
the
bright red, wiggling strings angled up steeply are a good visual stall
warning.

That must be true only for unflapped gliders, or it's valid only for
one specific flap setting in a flapped glider. Or you have to make
different coloured markings for each and every flap setting.

Aldo Cernezzi

You're right about flaps making a difference in the calibration. I've only
tried this on two flapped gliders and one without flaps. However, It seemed
to work pretty well in all cases. I actually didn't see too much difference
in the string indications at different flap settings.

The flap issue is partly moot since the flap settings are related to
airspeed bands. Stall concerns would likely arise only with the flaps in
their most positive two settings, landing or slow thermalling. The
near-stall indication is very obvious.

Bill Daniels

Bill,

Are you still using the AOA indicators made from yaw strings? Which
glider type is it mounted on?

I assume these strings would be forward, so you visualize them at the
same time you see the normal yaw string. Is that correct?

John

"John" wrote in message
om...
Bill,

Are you still using the AOA indicators made from yaw strings? Which
glider type is it mounted on?

I have tended to use them with new gliders to calibrate my seat of the pants
feel near a stall. Once my senses are atuned to the glider the strings are
no longer neccessary. I have tried them on a Lark IS28, Blanik L-23 and a
Nimbus 2C. The string indications were simular on all.

I assume these strings would be forward, so you visualize them at the
same time you see the normal yaw string. Is that correct?

The strings need to be as far forward as possible to get away from the
near-field flow over the wing. If I recall my Aerodynamics 101, the perfect
place for an AOA sensor would be about 10 wing chord lengths ahead of the LE
on a nose boom. The best practical position is near the forward end of the
canopy side frames. This happens to put them in the pilots field of view.

The 3D flow over the glider's nose seems to amplify the response of the
strings to changes in AOA so don't expect the string angles to represent the
actual AOA. While the absolute accuracy is terrible, the indications are
very repeatable and once calibrated to the three critical AOA's, they do
give useful data.

The biggest problem is that they are highly sensitive to yaw angles but if
both strings are giving the same indication, the yaw error is cancelled out.
Another nuisance issue is that the strings tend to get sucked under the
canopy frame as it is being closed trapping the strings.

Bill Daniels

Bill Daniels wrote:

"cernauta" wrote in message
...

"Bill Daniels" wrote:


Tape two yaw strings (which then become pitch strings) on each side of

the

canopy at the lowest and most forward part you can still see.

The string angle difference between minimum sink and stall is large so

the

bright red, wiggling strings angled up steeply are a good visual stall
warning.

That must be true only for unflapped gliders, or it's valid only for
one specific flap setting in a flapped glider. Or you have to make
different coloured markings for each and every flap setting.

Aldo Cernezzi


You're right about flaps making a difference in the calibration. I've only
tried this on two flapped gliders and one without flaps. However, It seemed
to work pretty well in all cases. I actually didn't see too much difference
in the string indications at different flap settings.

The flap issue is partly moot since the flap settings are related to
airspeed bands. Stall concerns would likely arise only with the flaps in
their most positive two settings, landing or slow thermalling. The
near-stall indication is very obvious.

Have you tried these in a shallow turning stall, when it is the wing tip
that stalls, not the root?

--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

"Eric Greenwell" wrote in message
...


Have you tried these in a shallow turning stall, when it is the wing tip
that stalls, not the root?


Yep, and the indication is still useful. No doubt the AOA measured near the
centerline is lower than the actual AOA of the inside wingtip. (Your point,
Eric.)

But, the AOA indication you do get is significantly greater than minimum
sink so that you would take it as a stall warning, or at least an indication
that lowering the nose would result in better performance.

YMMV, but my experience with them has been that the 10cm long strings are
25mm or so higher at stall than at min sink while the difference between
best L/D and min sink is only 5 - 10mm. The strings angle upward and wiggle
a lot near stall.

All I can say is try it. If it doesn't do anything for you, rip 'em off.
It's a pretty cheap experiment.

Bill Daniels

"Bill Daniels" wrote in message ...

All I can say is try it. If it doesn't do anything for you, rip 'em off.
It's a pretty cheap experiment.

Bill Daniels


A few years ago I tried the same thing on an LS4. It worked, but was
so sensitive to yaw that the readings were not very useful.

I still wish I could have an audio AOA tone with the gear down (and
matched to the flap setting) that would indicate whether I was fast,
on-speed, slow, or REALLY SLOW (just like the good old F-4). Just
having a stall indication is unfortunately only giving the pilot some
of the information he really needs. And having an accurate audio tone
would allow the pilot to keep a lot more attention outside the cockpit
during the landing pattern (which is kinda nice).

It's really AOA that we fly when slow anyway, using airspeed as an
approximation...

Nice thing about AOA instead of airspeed is that it automatically
compensates for weight, so landing back immediatly after takeoff full
of water (rope break, aborted winch launch) would be a lot safer.

With the gear up, no audio but the AOA for min sink (regardless of
ballast and bank angle and adjusted for flap position), L/D max, and
best acceleration/min drag (when pushing out of a thermal) could be
shown with individual LEDs or a simple edge indicator, to give the
pilot an idea how he is optimizing his flying.

How about it, some smart person? I guarantee, once you fly AOA, you'll
never go back to chasing the ASI!

Kirk

Speaking of simple warning devices:
How about a simple hookup to a horn which is activated when the
airbrakes are opened while the towhook is engaged (i.e. open spoilers
during tow)?
A microswitch on the airbrake levers would be the no-brainer part.
What about the towhook? Magnetic sensor? where? How? Other ideas?
Uri

(Mark James Boyd) wrote in message news:4054b43e$1@darkstar...
Robertmudd1u wrote:

Some may think this a cheap shot, but what the heck.

Believe it or not some pilots fly gliders with fixed gear. They even fly them
X-C and make land outs. They even stall/spin them.

Too many people in this sport think you need ALL the bells and whistles and a
$100,000+ glider to be a "real" glider pilot. That attitude is hurting us.

Robert Mudd

I certainly would not use the word "need" with respect to a
glider AOA indicator.

And yes, cheap and simple is important. Perhaps the cheapest idea
is simply the ol' harmonica style Cezzna AOA indicators, one
mounted on each wingtip of a 1-26 (easier to install on a metal wing,
and the 1-26 is a glider with more than it's share of stalls
leading to fatalities).

Then, if added complexity is warranted, a small switch on the
spoilers which deactivates the audio vario when the spoilers are out,
so one can now just barely hear the stall horns.

Ideally, it would be nice to have removable wingtips, so
one could experiment without modifying a whole wing...

Perhaps there are other types that would have this feature
to allow inexpensive experimentation. Then maybe try the electric
AOA tabs too...